Interface Engineering by Thiazolium Iodide Passivation Towards Reduced Thermal Diffusion and Performance Improvement in Perovskite Solar Cells

Interface engineering has become one of the facile and effective approach to improve solar cells performance, its long-term stability and retard unwanted side reaction. We have developed three passivating agents which can functionalize the surface and induce hydrophobicity by employing substituted thiazolium iodide (TMI) for perovskite solar cells fabrication. The role of TMI interfacial layers on microstructure and electro-optical properties was assessed for structural as well as transient absorption (TA) measurements. TMI treatment resulted into V_OC and FF enhancement by reducing possible recombination paths at perovskite/HTM interface and by reducing the shallow as well as deep traps. These in turn allowed to achieve higher performance as compared to the pristine surface. Additionally, TMI passivated perovskite layer reduces considerably CH₃NH₃⁺ thermal diffusion and degradation induced by humidity. The un-encapsulated perovskite solar cells employing TMI exhibited a remarkable stability under moisture levels (~50% RH) retaining ~95% of initial PCE after 800 h of fabrication, paving potential scalable endeavour.